The Eternal Doctrine is how most species refer to the Ur-Quan Kohr-Ah's alternative philosophy to the Ur-Quan Kzer-Za's Path of Now and Forever. It stipulates that to eliminate any future threat to Ur-Quan freedom all non-Ur-Quan sentient species are to be exterminated. While the Kzer-Za, the Melnorme, and most Human sources use the term "Eternal Doctrine", the Kohr-Ah themselves never use this phrase to describe their philosophy, instead calling it the "Path of Now and Forever".

The Black Ur-Quan, as the warriors they were, found themselves unable to accept the Path of Now and Forever created by the Kzer-Za following the victory of the Ur-Quan slave revolt. A charismatic leader, Kohr-Ah, stepped forward to declare a doctrine that renounced the Kzer-Za's plan to mimic the Dnyarri in becoming slave masters, which the Black Ur-Quan saw as demeaning and useless. Instead, they decided to take the bold step of simply destroying sentient life where they found it, eliminating all potential threats.

The first race to fall victim to this philosophy was the Yuptar, a former member of the Sentient Milieu, only just freed from the Dnyarri slave empire by the Ur-Quan's revolt. After incinerating the Yuptar homeworld, the Kohr-Ah traveled to the homeworld of the only other remaining Milieu race, the Mael-Num. However, the Mael-Num, having learned of the Kohr-Ah's intention and unable to resist them, broadcast a single, plaintive plea for an explanation. The Kohr-Ah were so moved by this helpless gesture that they felt compelled to halt their advance and argue the case for their beliefs to the Mael-Num. While they were thus detained the Kzer-Za intercepted their advance and began contradicting their argument, making a case for their Path of Now and Forever and stating their absolute opposition to the crime of genocide. In the confusion, the two opposing factions broke out into the first Doctrinal War, and the Mael-Num escaped.

Such was the emotional impact of the Mael-Num's plea, known to them simply as "the Words", on the two Ur-Quan cultures that many generations later, any repetition of the Words — usually translated in English as "Hold! What you are doing to us is wrong! Why are you doing this thing?" — is enough to force the Ur-Quan to halt their actions and justify them, though the Kohr-Ah's emotional reaction to the Words seems far more intense than the Kzer-Za's.

After the Kohr-Ah lost the first Doctrinal War, they were forced to let the Kzer-Za pursue their Path of Now and Forever on a spinward path through the galaxy without interference, while they traveled anti-spinward pursuing what they themselves refer to as the Path of Now and Forever but the Kzer-Za refer to only as the Eternal Doctrine. The Kohr-Ah have ruthlessly slaughtered over five thousand civilizations throughout a large portion of the galaxy before they are stopped, at the end of Star Control II, by the combined might of the New Alliance of Free Stars.

The Kohr-Ah's Eternal Doctrine is much simpler and less subtle than the byzantine Path of Now and Forever of their "effete" Kzer-Za brothers. The Kohr-Ah religiously ignore any pragmatical or moral objections to their philosophy, which they consider self-justifying, needing no confirmation. They also believe in reincarnation, that all sentient life is in a constant cycle of death and rebirth into new forms. Since the death of an individual is the not the end of its existence, termination of life has no adverse effects, but in fact provides a sentient being with an opportunity to be reborn as an Ur-Quan. All other forms of life (with the exception of the Kzer-Za, their "partners in the eternal conflict", the only race they consider an enemy) are considered "filth" — possible future threats to the freedom and security of the Ur-Quan species — or "threats" — a status that The Captain may receive after destroying a certain number of Marauders. Both filth and threats must be cleansed. The only exception allowed is the case of an alien race which agrees to kill every non-Ur-Quan sentient life-form, including themselves — a condition that no one has ever accepted.